Vegetable oil refining



United States Patent VEGETABLE OIL REFINING Hans Wolif and Lester P.Hayes, Decatur, 111., assignors to A. E. Staley Manufacturing Company,Decatur, 111., a corporation of-Delaware No Drawing. Application March4, 1953,

' Serial No. 340,388

12 Claims. 01. 260-424) This invention relates, generally, toinnovations and improvements in the refining of vegetable oils. Moreparticularly, the invention pertains to the use of ketene as a degummingagent for lecithin-bearing vegetable oils, such as soybean oil,cottonseed oil, perilla oil, linseed oil, peanut oil, corn oil and tungoil whereby such oils can be rendered both heat break-free and acidbreak-free. The break-free vegetable oils provided by this invention aresuitable for edible and industrial purposes requiring vegetable oils ofthe highest quality.

Crude vegetableoils of the class referred to above contain substanceswhich in contact with water tend to settle. out or separate from themain body of the oil. Such substances are commonly referred to anddesignated as gum or gums and they are obtained in the commercialrefining of vegetable oils, such as crude soybean oil, by the additionof water to the crude oil followed by centrifuging the mixture toseparate the water component containing the gums from the main body ofthe oil. These gums, after drying, and in certain instances after knownadditional treatments, are marketed commercially as lecithin.

The separation of the gums or lecithins is carried out not only becauseof the commercial value of these substances as by-products but alsobecause their presence in the oil is undesirable for most of theultimate uses made of the oils. However, the water degumming treatmentnormally does not remove the final traces of lecithin or othergum-forming substances. The residual amounts. of these substancesremaining in the oil, even though small, are suficient to cause adarkening and clouding of the oils on heating, usually with theformation of a visible black flock. This flock is commonly known andreferred to in the art as break and an oil which shows suchfluocculation or darkening on heating is considered to contain break.

If an oil on heating to 550 F. shows no darkening or flock but on thecontrary tends to get lighter, i. e. heat bleaches, such an oil isconsidered to be heat break-free oil or a non-break oil. In addition, ifthe oil on heating. to 550 F. in the presence of hydrochloric acid showsno darkening or flock but lightens in color, it is considered to be anacid break-free or Gardner break-free oil according to. American OilChemists Society, Oflicial Method Ca 40, May, 1949.

The so-called break in industrial oils is undesirable because itinterferes with various processing operations and shows up adversely infinished products. For example, large quantities of soybean oil are usedby the paint and varnish industry, one of the principal uses thereinbeing in the preparation of alkyd resins. These resins are usedextensively in making white enamels (e. g. refrigerator enamels) andother high grade industrialfinishes and any break in the oil tends todarken and detract from the white color of such finishes.

' Break is also. undesirable when degummed vegetable oils are used formaking edible oils since the, production of edible vegetable oilsusually involves a deodorization 2,754,309 Patented July 10-, 1956 stepwherein the oils are heated in the presence of steam to temperatures of350-500 F. at pressures substantially below atmospheric. If there isbreak in the oils when they are deodorized in such a manner, they turndarkand their flavor is adversely affected.

Heretofore, the most extensively used technique for obtaining break-freevegetable oils has been the so-called alkali-refining process.Essentially this process consists of Washing either the crude oil or thewater degummed oil with aqueous caustic solution. The byproduct of thisalkali-refining operation is referred to as soapstock and is a darkgreasy substance consisting mainly of a mixture of soaps, neutral oiland water. The alkali-refining technique entails loss of valuableneutral oil, partly by entrainment of the neutral oil in the soapstockand partly by hydrolysis of the neutral oil.

In addition to the alkali-refining technique, a number of other methodshave been proposed for obtaining breakfree oils but insofar as has beenlearned, such methods have not been adopted in the industry. Patent No.2,410,926, dated November 12, 1946, for example, mentions sulfarnic,oxalic, citric, picric'and maleic acids as being useful degumming agentsfor obtaining breakfree oils. Patent No. 2,448,434, dated August 31,1948, discloses the use of halogenated lowaliphatic acids as degummingagents for use in preparing break-free vegetable oils. None of thedegumming agents disclosed in these. patents has proven to becommercially successful for one reason or another.

It has been found according to the present invention that the use. ofketene in the process of water degumming vegetable oils permits theeconomic production of; breakfree oils and ofiers unexpected advantagesover the methods used and suggested in the prior art. The first memberof the. group of ketenes is itself known as ketene and has theformulaCHzzCO. Ketene is readily available and. can be made on a commercialscale by known methods, such as by cracking or pyrolyzing acetone. Thiscompound is a gas at ordinary temperatures.

The present invention offers the following advantages and improvementsover the conventional alkali-refining process for refining vegetableoils to obtain break-free oils:

(1) The. break-free oils maynow be obtained in the degumming operation.alone and no additional refining step is required, whereas-alkalirefining involves an added step over andabove the degumming treatment.

(2) Fatty acids can now be recovered in a single step as oncedistilledfatty acids during thedeodorization operation. These fatty acids aremuch more valuable than the soapstock obtained in the alkali-refiningtechnique from which pure fatty acids can be recovered only in atwo-step separation, i. e. acidification and distillation.

(3 The loss of neutral oil is substantially reduced because of theelimination of the separate alkali-refining step and because there islittle or no hydrolysis involved.

(4) The deodorizedbreak-free oil has excellent flavor and goodstability.

Certainother advantages of the invention will, in part, be obvious andwill, in. part, appear hereinafter.

One of theunexpected features of the, present invention is the fact thatbreak-free oils can normallybe made more efficiently from crudevegetable oils which havenot been either partially refined or allowed tostand long enough to permit a portion of the gums to settle out. Infact, the process of the present invention works better when used torefine-raw crude oils which have notv been allowed to stand or settle orrefinedin any way.

While vegetable oils broadly may be treated inaccordance with thepresent invention, especially lecithinbearing vegetable oils, it hasparticular utility inconnec tion with the treatment of. soybean oilsince soy lecithin is the most important commercial lecithin. Inaddition to soybean oil, other oils which may be treated to advantage inaccordance with the present invention are corn oil, cottonseed oil,peanut oil, linseed oil, perilla oil and tung oil.

An important object of the invention is an economical method ofobtaining heat and acid break-free vegetable oils, particularly soybeanoil, without the use of alkali, by treating the crude oil in a waterdegumming operationwith a very small quantity of ketene (CHzzCO).

Another object of the invention is a method of obtaining heat andbreak-free vegetable oils, particularly soybean oil, without theformation of soapstock, and with little or no loss of neutral oil whichcomprises incorporating in the water degumming step or in associationtherewith a small amount of ketene, agitating the mixture of water, oiland ketene for a suitable period, and then separating the aqueous phasefrom the oil by a suitable method, the resulting degummed oil being heatand acid break-free and of a quality useful for making edible oils ofsuperior flavor characteristics and for formulating white baked-onenamels and for other industrial uses.

Another object of the invention is an economical onestep method ofdegumming lecithin-bearing vegetable oils to render the same'both heatand acid break-free;

Another object of the invention is a method of degumminglecithin-bearing vegetable oils to render the same both heat and acidbreak-free which is especially eflicient in connection with oils whichhave not been partially degummed as the result of standing or partialrefining.

Still another object of the invention is an economical process of makingheat and acid break-free vegetable oils wherein fatty acids can berecovered during deodorization of the break-free oils as once-distilledfree fatty acids.

Other objects of the invention will, in part, be obvious, and will, inpart, appear hereinafter.

The process of the present invention involves incorporating a minoramount of ketene into a vegetable oil and then subjecting the oil toaqueous degumming treatment. The amount of ketene added may be as littleas 0.015% by weight based on the weight of the oil and the particularamount added in any refining operation will depend upon the times andtemperatures employed. In generab'when higher temperatures are employed,i. e.

60400 C., the times of treatment may be shorter and a the quantities ofketene used may be smaller, whereas at lower temperatures, e. g. 30 60C., longer times are required and higher concentrations of ketene shouldbe used. Accordingly, it will beseen that the concentrations of keteneused, the periods of treatment and the temperatures employed are factorswhich may vary within rather wide limits and there is a relatively widerange of particular conditions or combinations which are useful and givesatisfactory results. In general, the preferred temperature range isfrom 6085 C. and preferably the ketene is added to the oil in aconcentration of approximately 0.015-0.02% based on the weight of theoil. The ketene may be added to the oil rapidly either before or afterthe water is added, and the mixture stirred or agitated; The duration ofthe treatment is not critical but should be kept as short as practicalin the interest of economy. The period of treatment will usually runfrom to minutes.

Full crude vegetable oils which have not been partially refined eitherby a refining treatment or by standing so as to allow the gums to settleout, respond more effivciently to the process of the present inventionthan do partially refined vegetable oils. In fact, full crude'vegetableoils containing on the order'of 0.5% break require smaller amounts ofthe ketene than do partially refined vegetable oils containing smallerbreak contents The following specific examples will serve iurther toExample 1 Ketene gas (CH2:CO) was generated according to the procedureoutlined on page 122, vol. 5 of Journal of Organic Chemistry (1940), J.W. Williams and C. D. Hurd. The ketene stream was standardized bypassing it for a given time through one normal aqueous solution ofsodium hydroxide and back-titrating the amount of sodium hydroxide notneutralized.

The stream of ketene was introduced into 500 ml. of solvent extractedsoybean oil at 60 .C. The oil contained 0.52% of break according to theGardner test. The oil was vigorously stirred during the addition of theketene which was allowed to continue for approximately. seconds beforeit was stopped. During this addition,

0.065 gram of ketene was passed through 450 grams of V the oil. This isthe equivalent to the addition of 0.014% of ketene based on the weightof the oil. To the oil thus treated with ketene was added 6.75 grams ofwater (1.5% based on the weight of the oil) with mild stirring. Afterstirring the mixture for 15 minutes at a temperature of C., the mixturewas placed in a centrifuge and the oil phase was separated from theaqueous phase. The resulting oil was break-free according to both theheat break test and the Gardner break test. The oil was bleached in theusual manner with bleaching clays and active carbon and then deodorizedat a temperature of a 225 C. at a pressure of 4 ml. of mercury. Prior todeodorization the break-free oil had a free fatty acid content of 0.32%and after deodorization the free fatty acid content was 0.008%. The freefatty acids were recovered from the distillate.

The oil that was obtained was first quality edible soybean oil. Thelecithin that was obtained on drying the gums from the separated aqueousphase was of good quality and was equal to the lecithin obtained by theconventional water degumrning process.

Example 2 To 500 ml. ofextracted soybean oil 7.5 grams of water wasadded. While the mixture was vigorously agitated, a stream of ketene waspassed through the mixture for 160 seconds at 60 C. (0.26 gram of keteneor 0.058% on the basis of the weight of the'oil). As soon as theaddition of the ketene was discontinued, the agitation of the mixturewas stopped and the mixture was centrifuged so as to separate theaqueous phase'from the oil. The oil that was obtained was break-free andof good quality.

Example 4 The process of Example 3 was repeated but the keteneintroduction was stopped afteronly seconds (0.13 gram of ketene or0.026%). The oil that was obtained was not'break-free.

Example 5 The process of Example 3 was repeated but at a lower"temperature of 30 C. The oil that was obtained was not break-free. Theprocess was repeated at 30 C. but

the ketene passage was prolonged to 220 seconds which yielded an oilthat was break-free.

Example 6 Through 500 m1. of crude corn oil ketene gas Was passed for160 seconds until 0.26 gram was added which is equivalent to 0.058% ofketene on the basis of the weight of the corn oil. The ketene wasintroduced in the oil while the oil was at a temperature of 60 C. 6.75grams of Water (1.5% of the weight of the oil) was then added to thecorn oil and the mixture was agitated for 15 minutes at 60 C. Themixture was then centrifuged and the oil obtained was break-free and ofgood quality.

Example 7 Ketene was passed through 500 ml. of crude peanut oil at 60 C.for 320 seconds until 0.12% ketene had been passed based on the weightof the oil. 1.5% of water based on the weight of the oil was added tothe oil and the mixture was stirred for 15 minutes and then centrifuged.The oil obtained was break-free and of good quality.

Example 8 The procedure of Example 7 was repeated but the addition ofthe ketene was discontinued after 160 seconds. The oil that was obtainedwas not break-free.

The methods of the present invention may be carried out in known typeequipment, either as a batch process or as a continuous process.

In view of the foregoing disclosure, those skilled in the art will beable to practice the invention either according to the specificembodiments and directions set forth above, or according to otherembodiments which will be obvious. Accordingly, all matter set forthabove is intended to be interpreted as illustrative and not in alimiting sense.

What is claimed as new is:

1. In the process of degumming a vegetable oil by treating the oil withwater and thereafter separating the aqueous gum-containing phase fromthe oil phase, the improvement which comprises, treating the oil with afraction of one per cent by weight of ketene while the oil is beingtreated with water.

2. The method of refining a vegetable oil so as to degum the same andobtain a break-free oil which comprises, intimately mixing with thevegetable oil suificient water for degumming and a fraction of one percent by weight of ketene, and separating the resulting aqueous phasefrom the oil phase.

3. The method of refining a vegetable oil so as to degum the same andobtain a break-free oil which comprises, introducing into the oil in arelatively short period of time a fraction of one per cent by weight ofketene, thereafter mixing the oil with sufficient water for degummingfor a relatively longer period, and separating the resulting aqueousphase from the break-free oil phase.

4. The method of refining a lecithin-bearing vegetable oil so as todegum the same and render it break-free which comprises, intimatelyadmixing with the oil a small percentage of water and a fractional percent of ketene based on the weight of the oil, agitating the mixture ofoil, water and ketene until the aqueous phase will readily separate fromthe oil phase, and separating the said phases.

5. The method of refining a lecithin-bearing vegetable oil so as todegum the same and render it break-free which comprises, intimatelyadmixing with the oil at a temperature in the range of about 30100 C. ofat least about 0.015% of ketene and at least about 1.5% of water basedon the weight of the oil, agitating the mixture until the aqueous phasewill readily separate from the oil phase, and separating the saidphases.

6. In the process of degumming soybean oil by treating the oil withwater and thereafter separating the aqueous gum-containing phase fromthe oil phase, the improvement which comprises, treating the oil with afraction of one per cent by weight of ketene while the oil is beingtreated with water.

7. The method of refining soybean oil so as to degum the same and obtaina break-free oil which comprises, intimately mixing with the soybean oilsufiicient water for degumming and a fraction of one per cent by Weightof ketene, and separating the resulting aqueous phase from the oilphase.

8. The method of refining soybean oil so as to degum the same and obtaina break-free oil which comprises, introducing into the oil in arelatively short period of time a fraction of one per cent by weight ofketene, thereafter mixing the oil with sufiicient Water for degummingfor a relatively longer period, and separating the resulting aqueousphase from the break-free oil phase.

9. The method of refining soybean oil so as to degum the same and renderit break-free which comprises, intimately admixing with the oil a smallpercentage of water and a fractional per cent of ketene based on theweight of the oil, agitating the mixture of oil, water and ketene untilthe aqueous phase will readily separate from the oil phase, andseparating the said phases.

10. The method of refining soybean oil so as to degum the same andrender it break-free which comprises, inti mately admixing with the oilat a temperature in the range of about 30100 C. of at least about 0.051%of ketene and at least about 1.5 of water based on the weight of theoil, agitating the mixture until the aqueous phase will readily separatefrom the oil phase, and separating the said phases.

11. The method of refining a lecithin-bearing vegetable oil so as todegum the same and render it break-free which comprises, intimatelyadmixing with the oil a small percentage of water and a fractional percent of ketene based on the weight of the oil, agitating the mixture ofoil, water and ketene until the aqueous phase will readily separate fromthe oil phase, separating the said phases, deodorizing the separated oilwith steam at elevated temperature and subatmospheric pressure, andrecovering the distillate containing steam-distilled fatty material.

12. The method of refining soybean oil so as to degum the same andrender it break-free which comprises, intimately admixing with the oil asmall percentage of water and a fractional per cent of ketene based onthe weight of the oil, agitating the mixture of oil, Water and keteneuntil the aqueous phase will readily separate from the oil phase,separating the said phases, deodorizing the separated oil with steam atelevated temperature and subatmospheric pressure, and recovering thedistillate containing steam-distilled fatty material.

References Cited in the file of this patent UNITED STATES PATENTS

1. IN THE PROCESS OF DEGUMMING A VEGETABLE OIL BY TREATING THE OIL WITHWATER AND THEREAFTER SEPARATING THE AQUEOUS GUM-CONTAINING PHASE FROMTHE OIL PHASE, THE IMPROVEMENT WHICH COMPRISES, TREATING THE OIL WITH AFRACTION OF ONE PER CENT BY WEIGHT OF KETENE WHILE THE OIL IS BEINGTREATED WITH WATER.